Rebound preventing type bar rest for typewriting machines



June 9, 1953 H. J. KISTNER 2,641,349

REBOUND PREVENTING TYPE BAR REST I FOR TYPEWRITING MACHINES Filed April .27, 1950 INVENTOR- HJ. KISTN-ER ATTORNEY Patented June 9, 1953 UNITED STATES PATENT OFFICE O Nfi. REST FOR; TYPEWRITING MACHINES Harem .i. K istiien Ehdicott; N. 1%,- assigiio'r: to International Business Machines Corporation; New York, N; Yr, a corporation of New York Asisiieation Aiifiil 27, 1950, serial No. 158,525

1 rhis application relates to improvements in oifiee machines, such as; t pewriters.

The broad" object of the present invention is to provide a simple and fiotive means of pre Venting" rebound of the type bars. v

Anobieo'tzis to provide a means of preventin rebound whieh does not require any mechanicaI connections to type" bars or the operatin trains therefor.-

Ail object is to provide means of preventing re sound which influences all of the type bars equally so as to simplify the problem of adjnst= iiig the type bars for even imprint.

An object isto" provide ameans of preventing rebound which contem lates theuse of a magnet to? restraining the type bar in its rest position. object is to provide a combined rebound preventing r'rieai is aridi-elio'und cushion.

Other objects of the invention will be pointed out the following description anti claims and illustrated in the accompanying drawings, which disclose,- by way of exam le, the prizieiple of the invention andthe best mode, which has been contempiateei; of applying that principle.

in the drawings:

- Fig. I is a section throuehthe newer operated type bar mechanism of an ofiioe machine.

- Fig. 2' is a perspective showing a nortionof the combined tyne bar eushi'en and rebound pre venting means.-

In the drawing there is disclosed a power 015-" izttd type bar mechanism Similar to the one disclosed. in Patefit; No. 2,046,082 Which discloses a well known machine for perforating accounting and statistical record cards and also typing on the top edge of such cards theinterpietatiori of the perforations which may consist of either num.. bi s or the letters at the alphabet. It will be ii'n' tiei stoocl', however; that the invention may be employed inother machines, such as convehtionalty ewri-ters, since the means for preventing re-- bo'urid is associatedwiththe type bar mechanism and. this mechanism, as disclosed in the above mentioned patent, is' more or less conventional in general features of construction and similar to the type bar mechanisms of irifell" known typewritei s.

The type bats are pivotally mounted on a iaiemm- Wire H iii a, cnrvedsegment !2, som moi-11 Known in the art as a wire segmentbe sensethe pivot" it is fact a wire curved to con: foam to the shape of the segment 12. only one type has it is shownin Fig. 1, but it will be u'iiderstood that, iii accordance with usna-lpractice, the segment l2 curved so that the tyiie'hais it are mounted horizontally in a oylifid'rial ar my. ijaeh type has is slotted at llla to reeeive a bin it carried by a sub' lever l3 pivoted 0Y1 the fuier'um wire it. This fulcrum Wire is suitably supported by a cross frame member is supp 'r't ed by the side plates [6 forming part ofthen seamen/on: of the machine; cooperating with the shorter arm of the sub le'ir'i I3 is ah enema ing lever eair'yirigthe pih 15d \t/"liiiil'l coopotates with the edge of the short arm of lev'r' l3. The lever it? is pivoted oil a fiiliuii'i Wire ll suitably supportedin the tramewens andat its lower end, the lever it has pivoted thelitfi at I55 an operatinghook I8; This hook has all-1g [8a capable of engaging a continuously rotating power roller 39 which turns iii a clockwise directionwhile the niaohine is in use.

The operating hooks [8' are ontrol-ld by the character keys 2!? which are pivot-ea on the fill-'- cruin wire 2-! suitably supported in the frame work. The keys 25: have downware extensions 2601 each of which normally overlies a his i819" on an associatedoperatiii'g" hook is to prevent a tension spring 22 interposed between the lower end of the lei/er IE and an extension of the hook i8 from rocking the hook l3 clo'ktvi-seto' engage the lug I861 with the pc 'iwi statue-tor IS. The tak tensions 2% are held iii alignment with the lugs itb a comb 23 suitably mounted in the traine wona Als'o pivoted on the fulcrum wire 2|, one" for each key 20, are the non rep'eat afiiis 2B2) each of which is onfieted to anas's'oitlted iitii'sion 29d by a spring 24 and the arms 2% are slightly lon er than the extensions ziiaso that normally the lower end of each extension 28b is a little be? low and. aligned with the too of the related 111g" [8b. The Keys 20 are held up against a resilient ste it by the springs 26.

When any key 29 is depressed, the extension-s 2e! are rocked to the right; thereby tensiomne the s ring it since the time 2071 cannot follow the: extensions ZBaVeI-y far and thereby the spring 22. is permitted to rock the hook f8 elokwis'to en a e the lug: I817, with the actuator it; There upon said actuator draws the hook is" to the left arm rocks the lever l5= clockwise. Pin lea; pressing dowii on the short arm of lever l3, rocks the latter oouritei 'clockWise and the pin l-3a trarisithi-t's this movement to the type bar It! as a clockwise rotation to drive the type bar to the prifiting position. In the above patent, the type bar strikes the top edge of the card (not shown) through a suite-tie inking ribbon (hot shoiirn) hut in a ton ventienait'freewri-ter the tyne bar Will makeits some form of type bar rest and rebound cushion is provided which in the past has been designed to cushion the shock of return of the type bar and damp the vibration thereof as quickly as possible. However, such devices have not been fluence of the magnetic flux decreases very rapidly with the increase in the air gap between the type bars i0 and the poles 21a of the magnet 21 in accordance with well known principles of magnetic theory. Once the magnetic force is overcome in operating the type bar, the type bar will be propelled with increasing acceleration to the printing position. On the return stroke of the type bar, as soon as the type bar comes within the magnetic field of the magnet I 21, the type bar is influenced by the magnet and wholly successful and in all machines having the disclosed type bar mechanism, the rebound of the type bars is a vexatious problem.

One of the difficulties arising from the rebound of the type bars is that it may be desired to use the same type bar a second time as in repeating characters and it sometimes happens that the power mechanism catches the type bar in part of an oscillation and starts to drive it to the printing position with the type bar already partly advanced to the printing position thereby causing the blow from a type bar which starts from an advanced position in such fashion to be different in strength from the blow starting from complete rest. Another difficulty is that a type bar may be in process of a rebound, particularly in the center of the type basket, while an adjacent one is in the initial stage of operation and the two sometimes collide and cause a jamming of the mechanism.

In order to avoid these difficulties, it is proposed to use a magnet which conveniently may take the form of a permanent magnet made from a very highly magnetic material such as now known under the name Alnico V which has the characteristics of very high magnetic strength with relatively small volume. In the drawings there is shown one illustrative form which such a magnet may take consisting of an 'arcuate channel shaped permanent magnet 21 which is disposed with its axis of cylindricity concentric with the axis of the cylindrical array of type barson the type segment I2 and disposed so that the poles of the magnet influence the type bars in a zone approximately one-third of the distance from the end to which the type element is fixed to the pivot wire H, the position of this zone not being critical. channel constitute the poles.

The type bars ill are prevented from touching the poles 21a of the magnet 27 by means of a rebound cushion 28 which is secured to the magnet 21 by any suitable means, such as cement, and is located half way between the poles of the magnet throughout the length of the magnet 21 which confronts the type bars. The height in cross section, with reference to Fig. 1, of the cushion 28 is greater than the depth of the channel in the magnet 2'] which forms the poles 27a of the magnet so that the type bars I0 normally are prevented from touching the poles. The cushion 28 may be made of any suitable resilient material such as rubber or plastic, which can withstand repeated blows, without materially losing its shape. Besides rubber there are a number of flexible plastics of which the well known Vinylite plastics are suitable.

The magnet 27 exerts a constant restraining force on the type bars H) which, however, is insufficient to prevent the power mechanism, comprising the power actuator I9 and the operating hook l8, from actuating a typebar and the in- The sides 21a of the v the restoring force of the type bar due to the efiectof the'various springs and the inertia of the-type bar itself is augmented by the magnetic field to restore the type bar against cushion 28 with a snap and the relatively great strength of the magnet in this position, once the power driving force is removed, is sufiicient to prevent the type bar from vibrating more than very slightly on the cushion .28.

It will be understood that while it is most convenient to use a permanent magnet to prevent rebound, it is contemplated that electromagnets might be used, if desired.

The cushion 28 serves several purposes. One

purpose is to produce a small gap between the poles of the magnet 21 and the type bars Ill so that it does not take an excessive amount of additional force to start the type bar away from the rest position, one that would be required if the magnet 21 were not present. On the return stroke of the type bar, the cushion 28 yields and allows the type bar to approach the poles of the magnet 21 more closely than in the rest position which, of course, greatly increases the effect of the magnetic field on the type bar with the result that, when the cushion 28 recovers from the shock of the blow, the type bar will be merely pushed back to, its rest position relatively more slowly without any appreciable amount of vibrations and without passing materially beyond its rest position. Within the space of the gap between the poles of the magnet 21 and the type bars I!) enforced by the cushion 28, the poles of the magnethave considerably greater strength than at a relatively short distance from the poles with the result that the damping effect on the type bars is quite considerable, yet each type bar is permitted to restore to a position where the power required to separate it from the magnet is not so great as to require a considerable increase in the power exerted by the power mechanism to propel the type bar to the printing position. While there have been shown and described and pointedv out the fundamental novel features of the invention, as applied to a preferred em-. bodiment, it will be understood that various omissions and substitutions and changes inthe form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only. as indicated by the scope of the following claims.

What is claimed is:

I. In a typewriting machine having a cylindrical array of type bars pivoted at their ends for a swinging movement inwardly from a rest position toward the axis of cylindricity to a printing position, rebound preventing means comprising a channel shaped permanent magnet disposed with its axis of cylindricity parallel with the axis of cylindricity of the type bars intermediate the ends of the latter and-normally holding said type bars in their rest position.

2. In a typewriting machine having a printing member and means to move said member from a rest position to a printing position, the combination of a magnet for yieldingly holding the printing member in its rest position, said magnet being weak enough to permit the moving means to dislodge said printing member from rest position, and non-magnetic means to space said member from said magnet in the rest position of said member and operative to cushion its restoring movement from printing position by introducing an air gap between said magnet and said printing member which air gap is reduced when the printing member strikes said spacing means at the end of said restoring movement.

3. The invention set forth in claim 2 in which the spacing means comprises a resilient rebound cushion yielding in the direction of restoring movement of said member to permit the latter to move closer to said magnet to momentarily increase the effect of the magnet on said memher.

4. The invention set forth in claim 2 in which the magnet comprises a bi-polar magnet of the horse-shoe type of which said member acts as an armature and the spacing means comprises a resilient rebound cushion located between the poles of the magnet.

5, The invention set forth in claim 1 provided with means normally to prevent the type bars from contacting the magnet when in their rest position and constructed to permit limited movement of the type bars from the rest position toward the poles of the magnet to cushion rebound a rest position to printing position, a magnet for holding the printing member in its rest position and operative to prevent rebound when the printing member is restored from the printing position, and yielding means to cushion rebound from the rest position located so that the rebound absorbing part of the stroke of the printing member is in a direction to temporarily increase the influence of the magnet, said yielding means forcing the printing member back torest position after the shock of rebound has been absorbed.

7. In a printing machine, a printing element movable from a rest position to a printing position and including a member having motion between two limits one of which corresponds to said rest position, means to move said member away from its rest position to efiect a printing stroke of said element, magnetic rebound preventing means strongly infiuencing said member in its rest position to resist movement of said member at the beginning of its printing stroke to a high degree but rapidly losing its influence with a small initial movement of said member away from rest position, and a yielding rebound cushion for controlling the influence of the preventing means when said member is restored to rest position.

HAROLD J. KISTNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 904,743 Weston Nov. 24, 1908 1,079,526 Vogel Nov. 25, 1913 FOREIGN PATENTS Number Country Date 7,339 Great Britain of 1899 

